Error while exporting a mesh from Blender Spark AR Toolkit V1.1.0
I also encountered this bug using the Blender 2.91. After some spelunking the the Toolkit's code and the Blender Python API I found a solution. Apparently something changed in the Blender export scene glTF API. When the Toolkit tries to export to glTF it passes the boolean value TRUE to the export_materials argument of the export function. However, it seems the export_materials argument no longer accepts a boolean value, but instead requires an enum value type. I tested it with the EXPORT enum value and that seemed to work fine.
I've already reported this to the Facebook Spark AR team and I expect an updated version of the Toolkit to be released in the near future. But if you really want to fix this now, you can do so by editing a Toolkit source file.
First close all running instances of Blender. Then locate the file spark_operators_export.py. It's location is mentioned in the error message that Blender displays. In your case it's /Users/kaiyawilson-smith/Library/Application Support/Blender/2.91/scripts/addons/Spark AR Toolkit/spark_operators_export.py. Edit that file using a plain text editor like Notepad.
Change line 66 from
export_materials=True,
to
export_materials='EXPORT',
Restart Blender and exporting your mesh should work again.